Copper(I) oxide
Copper oxide or cuprous oxide is the inorganic compound with the formula. It is one of the principal oxides of copper, the other being copper(II) oxide or cupric oxide. The compound can appear either yellow or red, depending on the size of the particles. Cuprous oxide is found as the mineral cuprite.
It is a component of some antifouling paints, and has other applications including some that exploit its property as a semiconductor.
Preparation
Copper oxide may be produced by several methods. Most straightforwardly, it arises via the oxidation of copper metal:Additives such as water and acids affect the rate as well as the further oxidation to copper oxides. It is also produced commercially by reduction of copper solutions with sulfur dioxide.
Alternatively, it may be prepared via the reduction of copper(II) acetate with hydrazine:
Copper chloride solutions react with base to give the same material. In all cases, the color of the cuprous oxide is highly sensitive to the procedural details. degrades to copper oxide in moist air.
Formation of copper oxide is the basis of the Fehling's test and Benedict's test for reducing sugars. These sugars reduce an alkaline solution of a copper salt, giving a bright red precipitate of.
It forms on silver-plated copper parts exposed to moisture when the silver layer is porous or damaged. This kind of corrosion is known as red plague.
Properties
Like all copper compounds, cuprous oxide is diamagnetic. It does not readily hydrate to cuprous hydroxide.Copper oxide dissolves in concentrated ammonia solution to form the colourless complex, which is easily oxidized in air to the blue.
Cuprous oxide is attacked by acids. Hydrochloric acid gives the chloride complex. Sulfuric acid and nitric acid produce copper(II) sulfate and copper(II) nitrate, respectively.
Structure
Image:Cuprite-66649.jpg|thumb|left|110px|Large crystal of the mineral form of copper oxide.In terms of their coordination spheres, copper centres are 2-coordinated and the oxides are tetrahedral. crystallizes in a cubic structure with a lattice constant al =. The copper atoms arrange in a Bravais lattice fcc sublattice, the oxygen atoms in a bcc sublattice. One sublattice is shifted by a quarter of the body diagonal. The space group is Pnm, which includes the point group with full octahedral symmetry.
Applications
The dominant use of cuprous oxide is as a component of antifouling paints.Cuprous oxide is also commonly used as a pigment and a fungicide.
Semiconductor and related uses
Rectifier diodes based on this material have been used industrially as early as 1924, long before silicon became the standard. Copper oxide is also responsible for the pink color in a positive Benedict's test.In the history of semiconductor physics, Cu2O is one of the most studied materials. Many applications have been demonstrated first in this material:
- Semiconductor diodes
- Phonoritons
Another unusual feature of the ground state excitons is that all primary scattering mechanisms are known quantitatively. was the first substance where an entirely parameter-free model of absorption linewidth broadening by temperature could be established, allowing the corresponding absorption coefficient to be deduced. It can be shown using that the Kramers–Kronig relations do not apply to polaritons.
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